KEG Klockable Envelope Generator

stschoen · July 11, 2018, 6:34pm

KEG Clockable Envelope Generator

This is an Audulus recreation of one side of the 4ms PEG “Pingable Envelope Generator”. Like the original it is a combination of a sync-able LFO and AR/ASR envelope generator. The LFO frequency is determined either by using a Tap Tempo button or by feeding the KEG an external clock on the klock input. A multiply/divide control allows the user to set the internal LFO frequency to a multiple of the incoming clock from 8 to 1/8. The duration of the AR envelope is determined by the internal LFO. The relative duration of the attack and release (skew) and shape of the attack and release curves can also be adjusted.
There are two modes of operation, sync and async. In sync mode, the internal LFO remains synchronized with the incoming clock. A gate on the quantized (qnt) input will start an envelope on the next LFO clock. The envelope will repeat while the gate is high. If cycle is on and the incoming clock is divided, the internal LFO and envelope will be re-synced to the next incoming clock if the qnt input is high when the clock is received.
In async mode the envelope rise and fall duration is still determined by the internal LFO, but the LFO and envelope start point is no longer synced to the incoming clock. A gate on the async input enters async mode and will trigger an immediate envelope. If the gate is held high the envelope will sustain until the gate falls. To return to sync mode, apply a gate to the sync input or reset. See the 4ms documentation at: http://4mscompany.com/peg/manuals/PEG_manual_v4.3.pdf for further details.

I/O

Input	Signal Range	Notes
	`0-1 gate`	provides frequency and sync to the KEG. The KEG LFO frequency is set by the last two clocks received and in sync mode will synchronize with the klock signal
	`0-1 gate`	asyncronous trigger - causes the KEG to enter async mode and produces an immediate envelope. If the gate is held high the envelope will sustain. retriggering before the release has completed will immediately start a new envelope.
	`0-1 gate`	quantized trigger - causes the KEG to enter sync mode and produces an envelope at the beginning of the next KEG LFO clock. If the gate is held high, the envelope will repeat.
	`0-1 gate`	resets the KEG

Output	Signal Range	Notes
	`0-1 modulation`	envelope output - all envelopes begin and end at 0 and rise to 1 if not interrupted.
	`0-1 clock`	Internal LFO output
	`0-1 gate`	rise gate - high during the attack phase
	`0-1 gate`	fall gate - high during the release phase
	`floating point number`	internal LFO frequency

Controls

Control	Function	Notes
	`cycle switch`	switches cycle mode - when cycle mode is active the envelope will continue to repeat. The input inverts the button state when high.
	`skew control`	controls the ratio of attack and decay times. Goes from ramp to triangle to reverse ramp
	`tap tempo`	sets the internal LFO frequency by measuring the time between two taps. Disabled when klock is high.
	`clock divide/multiply`	adjusts the internal LFO frequency from 1/8 to 8 times the incoming clock.
	`rise segment curve`	adjusts the curve of the attack portion of the envelope from log to linear to exponential.
	`fall segment curve`	adjusts the curve of the release portion of the envelope from log to linear to exponential.

Displays

Meter	Displays	Notes
	`current multiply/divide factor`

Version History

Revision	File	Date	Notes
1.5	KEG Klockable Envelope Generator V1.5.audulus (123.2 KB)	07/17/2018	another rework of the gate logic to improve triggering.
1.4	superceded	07/15/2018	modified rise and fall gate logic so gates are only active during an envelope
1.3	superceded	07/15/2018	fixed quantized gate logic, improved ramp skew, reversed fall curve control to match label
1.2	superceded	07/11/2018	fixed divide by zero problem and reversed knob with skew control
1.1	superceded	07/11/2018	Fixed swapped curve controls
1.0	superceded	07/11/2018	Initial upload

Demos

Revision	File	Date	Notes
1.5	KEG - Klockable Envelope Generator Demo V1.5.audulus (1.0 MB)	07/17/2018	demo with KEG version 1.5
1.4	superceded	07/15/2018	KEG version 1.4
1.3	superseded	07/15/2018	initial upload - includes preliminary rotating clock generator module

robertsyrett · July 11, 2018, 7:14pm

Excellent!

I’ve already personalized mine for added faux symmetry.

stschoen · July 12, 2018, 11:14pm

Still working on the trigger logic. It’s a bit flakey at the moment. It’s a complex module and the switching is causing me some headaches. I think it can be worked out, but it might take me a bit of time. Patience is a virtue.

stschoen · July 15, 2018, 1:46pm

I think I finally got all the gate logic working. It was one of those tricky timing deals where it would work if a waveform node was attached then stop if you removed it. I included a preliminary version of the 4ms RCD (rotating clock divider). It works but still lacks some of the functionality of the original. (no spread mode). I want to get it closer to the original before I post it in modules. Let me know if you encounter any bugs in either module.

stschoen · July 15, 2018, 5:06pm

Still one “glitch” in the quantized gate logic. If the quantized gate is clocked by the same source as the klock input you would expect that the envelope would start on the current cycle rather than the next one, however this is not currently the case. If the qnt gate arrives at the same time as the klock, the envelope will be delayed to the next cycle. This leads to an envelope every second cycle rather than one per cycle as you would expect.

stschoen · July 17, 2018, 11:05pm

I think V1.5 is getting pretty close. I tried a lot of different approaches to creating a quantized gate. Turned out to be much more difficult than it first appeared. Since nothing in Audulus actually happens simultaneously, when you have logic signals that are very close in time, weird things begin to happen. This one seems pretty stable, but let me know if you find any anomalies.